In the concrete industry, large slabs of concrete are used to form road beds, building floors and other structures used for its strength and durability. Seams, grooves or other cuts in the concrete may be made in the slabs to form expansion joints, control stress cracks as the slabs cure or to form channels or openings in the slabs to accept other structures. Concrete saws are used to cut the seams, grooves or other openings, and such concrete saws are often very heavy and difficult to move along the concrete slab.
For large or heavy construction applications, heavy self-propelled saws or other large concrete saws are used. During setup and operation of the saw, an operator walks behind the saw to control the direction, cutting speed, cutting depth and other operating conditions under which the saw operates. The saw includes one or more wheels allowing the saw to move along the concrete and a frame supported by the wheels on which is mounted a motor or other power supply for operating a saw blade and often for driving one or more wheels to move the saw along the concrete surface. One or more handles extend behind the saw about the level of an operator's hands to allow the operator to manually position the saw. Typically, the saw blade is in the front of the saw and handles extend behind the saw. For a typical straight cut, the operator aligns the saw blade and often a cutting guide with the intended cutting path. The saw is maneuvered with the saw blade raised above the concrete until the blade and cutting guide are aligned with the cutting path. As the saw blade engages the concrete or other surface to be cut, the blade cuts into the concrete to the desired depth, such as the depth selected by the operator. At the desired depth, the drive wheels are engaged to propel the saw forward to cut the desired slot or groove, which typically follows a straight cut path.
Conventional self-propelled concrete saws have the cutting blade mounted on the left or right side of the machine, so that the saw blade is significantly offset from the center of the machine and supported by the frame of the saw. The drive wheels on the rear axle propel to machine by applying torque and rotation to the drive wheels. When the blade is cutting the work surface, the blade applies an opposite resisting force against the drive from the drive wheels, but the resisting force is off-center to the side of the frame center line.
When the wheels propel the saw forward and the blade is down and cutting on the right side of the saw, the saw tends to veer to the right. Correspondingly, when the blade is cutting on the left side of the saw, the saw tends to veer to the left. To compensate for the blade cutting resistance force created by the saw blade, the operator can physically lean on the handle bars to correct for the changing direction away from the cut path. However, such manual correction is not practical for larger saws or where it may be difficult for the operator to maneuver the saw.
A more efficient way to provide compensation is to align the rear axle to extend in a direction other than perpendicular to the center line of the frame, or in other words the cut path. Re-aligning the rear axle to be other than perpendicular produces a non-parallel propelling force in an attempt to compensate for the blade cutting resistance force produced by the blade while cutting, with the intention of producing a net straight-line movement of the saw along the cut path. Such a re-alignment may be performed manually or electrically, as described in the documents EP 1773557 and U.S. Pat. No. 7,669,589, which are incorporated by reference. Here, an example is provided where a toggle switch is used to steer a saw either to the left or to the right.
However, there is still a desire to further improve an alignment device for concrete saws of this kind.